The present invention relates to an apparatus for measuring and displaying the distances to obstructions behind a vehicle and, more particularly, to an ultrasonic obstruction detecting apparatus for measuring the time taken by ultrasonic waves emitted from the apparatus to return to it after reflection by the obstructions to determine the distances to the obstructions.
Conventional apparatuses of this kind consist of ultrasonic transmitting and receiving devices firmly fixed to the rear bumper of a vehicle and a display unit mounted in the interior of the vehicle for displaying the distances to obstructions in the form of bar graphs, for example. These apparatuses making use of ultrasonic waves are cheaper than television camera or the like and require less maintenance for removing dirt and dust. Further, these can be used even when it is raining or snowing or at night. Another advantage is that accurate measurement of distance is possible.
Unfortunately, the aforementioned ultrasonic obstruction detecting apparatuses need an array of ultrasonic transmitting and receiving devices of the same kind to sense the positions of obstructions in every region behind a vehicle. Accordingly, a large space is required to install the array of the devices, and such apparatuses are quite expensive to fabricate.